Phase separation tank

Phase separation tank

(D) Means for transferring aqueous liquid from the aqueous liquid outlet of the separation compartment to the aqueous liquid inlet of the aqueous compartment.
(C) An aqueous liquid compartment separated from the organic liquid compartment by an aqueous separator and separated from the separation compartment by the organic compartment, the aqueous liquid compartment equipped with an aqueous liquid inlet; and
(B) An organic liquid compartment separated from the separation compartment by an organic separator of a height that allows for the overflow of organic liquid from the separation compartment to the organic compartment;
(A) A separation compartment having a sloped bottom wall and an aqueous liquid outlet;
A phase separation tank for separating an aqueous liquid from an organic liquid, the tank comprising:

FIELD OF THE INVENTION

This invention relates to a process for the recovery of gold from anode slimes. In one aspect the invention relates to a continuous, completely hydrometallurgical process while in another aspect, the invention relates to a process employing improved mixing tank and phase separation tank designs.

BACKGROUND OF THE INVENTION

In the production of copper, copper-bearing ore is mined, concentrated, smelted and refined. The copper-bearing ore contains many other elements, including many other metals, that must be separated from the copper before the copper is ready for sale. Each step of the copper producing process involves separating these other elements from the copper until the copper reaches a desired sale purity, typically four “nines” purity, i.e., 99.99% copper.

The smelting stage of the copper producing process produces a copper anode which is typically three hundred plus pounds and 98+ percent copper. These anodes contain, among other elements, various metals some of which are quite valuable. In order to separate these other elements from the copper, these anodes are placed into a tank (or “electrolytic cell”) of electrolyte containing sulfuric acid and subjected to a direct current (DC). Under the influence of the electrolyte and electric current, the copper anode dissolves and the copper plates onto a stainless steel cathode to form a copper cathode of four nines purity. The other elements in the copper anode precipitate to the bottom of the tank and form “anode slimes”.

Among the components of the anode slimes are such valuable metals as gold and silver and over the years, much effort has been directed to their recovery. These efforts have included both pyrometallurgical and hydrometallurgical methods each of which has its own advantages and disadvantages.

One hydrometallurgical process of interest is that developed by Kennecott Utah Copper and first described by J. E. Hoffmann et al. at the 1995 International Conference of The Metallurgical Society of CIM, Hydrometallurgical Processing of Kennecott Refinery Slimes, COPPER 95-COBRE 95 (Vol. III). In this process a slurry of the slimes and water (or an aqueous solution of hydrochloric acid) is formed, and the slurry is vigorously agitated with chlorine or hydrogen peroxide (a procedure known as “wet chlorination”). The chlorinated (or liberated) gold is extracted from the resulting mixture in a multi-stage, countercurrent flow scheme in which dibutyl carbitol (DBC) is the extracting organic solvent. The gold-loaded DBC is then scrubbed with an aqueous acid wash to remove minor metal impurities, the gold reduced directly from the DBC, and recovered.

Variations on this theme have been developed over the years, e.g., U.S. Pat. No. 5,942,024, but the search for improvements continues. For example, a reduction in the footprint of the physical plant in which the process is conducted is desirable both from a capital and operating cost perspective and from the amount of gold held in ‘inventory”. The larger the physical plant, the costlier to build, operate and maintain the plant, and the more gold is held within the plant.

Another source for improvement is in the recovery of gold from the slimes. In the current process, some gold-loaded DBC is entrained in the aqueous phase of the extraction process, and this can result in a loss of 5 to 20 ppm gold in the raffinate. Any recovery of this “lost” gold can result in a marked improvement to the overall economics of the process.

SUMMARY

In one embodiment the invention is an apparatus for the recovery of gold from a gold-bearing filtrate, the apparatus comprising:
(A) A two-stage solvent extraction (S.E.) circuit comprising:
(1) A first S.E. mixing assembly;
(2) A first S.E. phase separation tank in fluid communication with the first S.E. mixing assembly;
(3) A second S.E. mixing assembly in fluid communication with the first S.E. phase separation tank; and
(4) A second S.E. phase separation tank in fluid communication with the S.E. second mixing assembly; and
(B) A four-stage acid scrub (A.S.) circuit comprising:
(1) A first A.S. mixing assembly;
(2) A first A.S. phase separation tank in fluid communication with the first A.S. mixing assembly;
(3) A second A.S. mixing assembly in fluid communication with the first A.S. phase separation tank;
(4) A second A.S. phase separation tank in fluid communication with the A.S. second mixing assembly;
(5) A third A.S. mixing assembly in fluid communication with the second A.S. phase separation tank;
(6) A third A.S. phase separation tank in fluid communication with the second A.S. mixing assembly;
(7) A fourth A.S. mixing assembly in fluid communication with the third A.S. phase separation tank; and
(8) A fourth A.S. phase separation tank in fluid communication with the fourth A.S. mixing assembly;
with the proviso that the second S.E. phase separation tank is in fluid communication with the first A.S. mixing assembly.

In one embodiment the invention is a process for the recovery of gold from an aqueous gold-bearing (Au-bearing) filtrate obtained from the wet chlorination of decopperized anode slimes, the process comprising the steps of:
(A) Contacting the aqueous Au-bearing filtrate with dibutyl carbitol (DBC) in a two-stage solvent extraction circuit to remove the gold from the aqueous Au-bearing filtrate into the DBC to form a gold-loaded DBC, the contacting performed in a manner such that the aqueous Au-bearing filtrate is contacted in the first stage of the solvent extraction circuit with DBC from the second stage of the solvent extraction circuit and fresh DBC is contacted in the second stage of the solvent extraction circuit with the aqueous Au-bearing filtrate from the first stage of the solvent extraction circuit; and
(B) Contacting the gold-loaded DBC from the second stage of the solvent extraction circuit with an aqueous acid scrub of greater than zero (>0) to 5 N hydrochloric acid in a four-stage acid scrub circuit to remove impurities from the gold-loaded DBC into the aqueous acid scrub to form an impurity-loaded aqueous scrub solution and an impurity-depleted DBC; the contacting conducted in a manner such that the gold-loaded DBC from the second stage of the solvent extraction circuit is contacted in the first stage of the aqueous acid scrub circuit with aqueous acid scrub from the third stage of the aqueous acid scrub circuit, and the gold-loaded DBC from the third stage of the aqueous acid scrub is contacted with fresh aqueous acid scrub in the fourth stage of the aqueous acid scrub circuit. In one embodiment the gold-loaded DBC leaving the fourth stage of the aqueous acid scrub circuit is contacted with a reducing agent to form metallic gold.

In one embodiment the invention is a mixing assembly for intimate contacting of an aqueous phase with an organic phase, e.g., an aqueous filtrate comprising chlorinated gold and an organic phase comprising DBC. In one embodiment the mixing assembly comprises:
(A) A vertical tank having a central vertical axis and comprising a side wall, a bottom inlet and an upper outlet;
(B) A mixing device comprising:
(1) A shaft having a top end and a bottom end;
(2) A variable frequency drive (VFD) motor attached to or near the top of the shaft in a manner to rotate the shaft when the motor is activated;
(3) An axial flow impeller disposed on the shaft and beneath the VFD motor;
(4) A radial flow plate disposed on the shaft and beneath the axial flow impeller; and
(5) A radial flow impeller disposed on the shaft and beneath the radial flow plate, the radial flow impeller not extending beyond the radial flow plate;
the mixing device fitted into the tank and along the central vertical axis of the tank such that the radial flow impeller is located closest to the bottom inlet and the axial flow impeller is located closest to the upper outlet;
(C) A baffle system attached to the side wall of the tank; and
(D) A liquid feed assembly connected to and in fluid communication with the bottom inlet of the tank, the liquid feed assembly comprising:
(1) A feed apparatus comprising top and bottom ends and a divider extending from the top end to the bottom end to divide the feed apparatus into first and second chambers, the top end of each chamber in fluid communication with the bottom inlet of the tank but neither chamber in fluid communication with the other chamber;
(2) A first feed pipe connected to and in fluid communication with the bottom end of the first chamber; and
(3) A second feed pipe connected to and in fluid communication with the bottom end of the second chamber.
The mixing assembly of this embodiment of the invention is not only useful in mixing the aqueous and organic phases of this invention, but it is also useful in transferring the organic/aqueous mixture from the first extraction stage to the second extraction stage, from the second extraction stage to the first settler stage, from the first settler stage to the second settler stage, and so forth.

In one embodiment the invention is a phase separation tank for separating an aqueous liquid from an organic liquid, the tank comprising a sloped bottom wall. In one embodiment the phase separation tank comprises:
(A) A separation compartment having a sloped bottom wall and an aqueous liquid outlet;
(B) An organic liquid compartment separated from the separation compartment by an organic separator of a height that allows for the overflow of organic liquid from the separation compartment to the organic compartment;
(C) An aqueous liquid compartment separated from the organic liquid compartment by an aqueous separator and separated from the separation compartment by the organic compartment, the aqueous liquid compartment equipped with an aqueous liquid inlet; and
(D) Means for transferring aqueous liquid from the aqueous liquid outlet of the separation compartment to the aqueous liquid inlet of the aqueous compartment.
The phase separation tank is useful in both the solvent extraction and aqueous acid scrub circuits of this invention.

How KEYWORD MONITOR works... a FREEservice from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Phase separation tank or other areas of interest.###

Data source: patent applications published in the public domain by the United States Patent and Trademark Office (USPTO). Information published here is for research/educational purposes only. FreshPatents is not affiliated with the USPTO, assignee companies, inventors, law firms or other assignees. Patent applications, documents and images may contain trademarks of the respective companies/authors. FreshPatents is not responsible for the accuracy, validity or otherwise contents of these public document patent application filings. When possible a complete PDF is provided, however, in some cases the presented document/images is an abstract or sampling of the full patent application for display purposes. FreshPatents.com Terms/Support -g2--0.4157